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The ditch does not cross any significant tributaries on the way to the reservoir from <br />which it would intercept natural flows. The irrigated acreage under the ditch above the <br />reservoir does not provide significant return flows that might be intercepted by the ditch. <br />Return Flow Locations: Seepage from the Boulder Larimer Ditch and irrigation return flows <br />accrue to the Little Thompson River along the natural topography underlying the irrigated <br />lands. There are no specific waste ways or similarly constructed conveyance structures <br />that collect and convey water directly back to the river. <br />Irrigated Crops: There are approximately 5,000 irrigated acres under the Boulder Larimer <br />Ditch system, based on SPDSS Draft Irrigated Parcel Mapping. The irrigated lands under <br />the New Ish Ditch generally commingle water from the Consolidated Home Supply Ditch <br />and/or Highland Ditch companies. <br />A representative crop mix under the ditch system includes the following: alfalfa (30 <br />percent), barley (30 percent), corn (30 percent) and sugar beets (10 percent). Smaller <br />amounts of small grains, vegetables and other crops are grown under the ditch and the <br />mix of crops irrigated is subject to change. According to ditch company representatives, <br />less than one percent of the lands under the Boulder Larimer Ditch system are sprinkler <br />irrigated. <br />HydroBase Data: The monthly data available in HydroBase over the 1950-2002 period of <br />record pertaining to the Boulder Larimer Ditch include the following: <br />Historical diversions through the Boulder Larimer Ditch are recorded in HydroBase <br />under Bould Larim Mfg Co D (0400588). Available diversions for the Boulder Larimer <br />Ditch average about 9,800 ac-ft per year (ac-ft/yr) over the 1950-2002 period. These <br />diversions include the following diversion classes (DivClass): <br />- Approximately 1,000 ac-ft/yr of direct diversions for irrigation 1950-2002, <br />- Approximately 3,000 ac-ft/yr of diversions to storage 1965-2002, <br />- Approximately 5,500 ac-ft/yr to 9,000 ac-ft/yr C-BT for irrigation 1953-2002, <br />- Direct use of C-BT water for irrigation has dropped from an <br />annual average of about 9,000 ac-ft in the 1950s and 1960s to <br />average less than 4,400 ac-ft in the 1990s. <br />- Approximately 1,600 ac-ft/yr C-BT to storage 1974-2001. <br />The records of direct diversions to irrigation and diversions to storage are generally <br />complete for the available periods of record listed above. The HydroBase records of <br />diversions to storage, C-BT for irrigation and C-BT to storage are listed under a <br />combination of various `From:' sources in the coding (2 for storage, 4 for C-BT for <br />irrigation and 5 for C-BT for storage). <br />2) Ish Reservoir (Structure ID 0404156) <br />Ish Reservoir is an off-channel storage facility located in Water District 4 approximately 3 miles <br />south of the Town of Berthoud. The reservoir was constructed from a natural lake in 1875 to <br />store irrigation water for late-season deliveries to irrigators under the ditch system. The reservoir <br />Boulder Larimer Ditch Memorandum.doc 5 of 11 October 28, 2004 <br />